The overall objective of the proposed studies is to determine the morphologic features and physiologic mechanisms which are responsible for the recovery process following acute renal injury. The models of acute renal injury to be studied include those of acute renal failure induced by dichromate administration, by bilateral renal artery occlusion and by ureteral ligation. The administration of ATP-magnesium chloride will be used to magnify and accelerate the course of recovery from each form of acute renal failure. The studies are designed to determine the factors responsible for the return of superficial single nephron inulin clearance prior to the return of the whole kidney inulin clearance. In addition, the effects of infusion of ATP-magnesium chloride after dichromate induced acute renal failure will be evaluated and compared to similar studies after a complete ureteral occlusion. To assess the role of prostaglandins in the recovery process the pattern of recovery will be observed following the administration of indomethacin.